German 36 342 058 and EP 0,261,379 describe a closable roof for a car having a one-piece rigid and stable roof element having when raised a generally horizontal upper roof region and side parts extending downwardly and back relative to the car and a pair of pivots on each of the two side parts or the rear of the roof that in a raised position of the roof are spaced apart somewhat below the vehicle body and that have a pair guide rails symmetrically on each of the two sides of the vehicle in which the pivots engage. The two guide rails of each pair have their upper ends spaced apart with the respective pivots and extend from there downward along similar paths so that their spacing decreases going down so as to produce an opening movement where the upper roof part is raised and then on further movement is dropped while generally vertical into its lower end position. The pivots in a first movement phase are moved in the guide rails downwardly along an arc so that the roof tips up with the upper roof part and the rear part pivots downward. The two rails that are fixed inside the car on the inside and that guide projections of the side parts via their pivots takes up quite a bit of space behind the seats and into the trunk area. Furthermore canting of the various guide elements is possible as a result of the difficult force distribution during opening and closing.
German 43 24 708 discloses a lowerable roof for cars, in particular for two-seater convertibles, having a shell forming a roof plate and rear roof posts and movable into a storage compartment between side walls of the vehicle body to which end it is oriented in a vehicle plane, forming a window opening for a rear window between a rear edge of the roof plate and the posts, and provided with guides for moving the roof plate and rear window so that the rear window can move from a lowered position relative to the roof plate into a lower position in which its edges are closely juxtaposed with the roof plate. The roof shell can drop down in lateral storage compartments via guides that are independent of the guides of the rear window and longitudinally slidable in the roof shell.
The two guide rails on the inner wall of the car that guide pivots or pins take up a great deal of space behind the seat and into the trunk area. In addition canting of the various guide elements is possible as a result of how the forces are applied during opening and closing. High surface pressures are created that make it difficult to operate the roof.
In addition German 40 38 074 describes a lowerable roof for cars, in particular a hard roof for a convertible, having roof posts to each side of a rear window of the roof that seen from the side with a storage position of the lower roof in a storage compartment in which the forward longitudinal regions of the roof form an obtuse angle underneath the roof posts and into which the roof can be lowered in which case the roof is tipped into the storage compartment. The rear window forms with the roof raised between the roof posts the rear part of the roof and can be moved from this position into a storage position in which with the roof lowered it is stowed above the lower ends of the roof posts. The roof is mounted on the motor-vehicle body by a pair of linkages that symmetrically flank the vehicle center plane and whose upper ends are pivoted at lower ends of the roof posts and that each include at least one guide link extending along an angled line to the rear window that is pivoted at its upper edge on the roof and at its lower end on the body of the vehicle. With this known solution parts of the passenger compartment are taken up by the lowering and raising process as a result of the relatively bulky linkages. The linkages are also mechanically expensive and failure-prone.
U.S. Pat. No. 2,191,269 describes a lowerable roof without rear posts for a convertible, wherein a raising and lowering mechanism formed by large and small rollers is provide that extends behind and partially below the seats. The raising and lowering mechanism is very likely to jam as a result of the roller drive and takes up all the space behind the seats.
All the known lowerable roof of the prior art achieve the required structural rigidity by being relatively massive, and are mechanically complex and expensive.